The present invention relates to a roof of a convertible as defined in the preamble of claim 1.
In prior art, specification EP 0835779 A1 presents a convertible roof divided into three substantially rigid roof sections, which are hinged on each other as a successive array in the longitudinal direction of the vehicle. Dividing the roof into three roof sections in the longitudinal direction of the vehicle is in itself an advantageous solution because the roof stowage space behind the passenger compartment thus takes up less of the trunk space of the vehicle, or if the trunk space is reduced, then the rear of the vehicle may be made shorter.
In the prior-art roof, the forward roof section, middle roof section and rearward roof section are constructed to be movable between a closed position and an open position. The free end of the forward roof section is provided with locking means to allow it to be fastened to the windscreen bar, which is a fixed part of the body, extending transversely between the A-pillars. In the closed position, the roof sections cover the passenger compartment of the convertible. In the open position, the roof has been folded down from its position over the passenger compartment into a roof stowage space behind the passenger compartment, the roof sections being laid in said space one over the other so that the forward roof section lies between the middle roof section and the rearward roof section. The rearward roof section is pivotally connected to the body of the convertible so that it can be turned by means of a main actuator. The middle roof section, which is pivotally connected to the rearward roof section, is connected via a mechanical pivoted lever system to the body and rearward roof section of the convertible so that the middle roof section is turned together with the rearward roof section by positive control when the roof is being turned between the closed position and the open position. The forward roof section is also connected to the aforesaid mechanical pivoted lever system so that the forward roof section is turned by positive mechanical control into a position under the middle roof section, between the middle roof section and the rearward roof section, when the roof is being opened.
All the roof sections, including the forward roof section, are turned by a single actuator, i.e. a hydraulic cylinder, acting on the rearward roof section, and the turning movement of the middle roof section and forward roof section is implemented using a mechanical positive control mechanism, in other words, lever arms pivoted on each other. The problem is that this mechanism becomes very complex and expensive.
The three-section hard roof known from specification EP 0 835 778 A1 was analyzed by a computer-aided method using a kinematics program that computes the paths of movement the lever system on the basis of the mathematical position of the pivots of the lever system. A problem thus detected was that very unfavorable leverage ratios of the lever arms develop in the positive control mechanism. This results in the generation of very large stresses, due to the dead weight of the roof, on the joints of the lever system and on different structural parts of the roof and its hydraulic system. This may lead to an increased play in the joints of the mechanism, which again may produce extra noises and problems regarding the sealing of the roof. If the roof mechanism according to said specification is to be so implemented that it will not rise to an excessive height when being opened or closed, or, on the other hand, so that the roof will not interfere with passengers in the passenger compartment during the movement, then it will be very difficult to optimize the leverages of the lever system according to the specification in respect of the stresses, and particularly strong materials need to used in the roof mechanism.
A further problem with the prior-art hard roof is that, due to the arrangement of the positive control mechanism of the forward roof section, the direction of motion of the main actuating cylinder has to be reversed at a certain point during the opening and closing movement of the roof. In other words, when the roof is being opened and lowered into the stowage space by retracting the piston rod of the main actuating cylinder into the cylinder and the rearward roof section has been lowered into the stowage space while the forward and middle roof sections are directly above the stowage space, the direction of motion of the piston rod has to be reversed and the piston rod has to be pushed outwards from the cylinder to turn the forward roof section against the middle roof section and to fold down the middle roof section over the rearward roof section so that the forward roof section simultaneously turns and goes between them. In practice, it is difficult to accomplish a timely reversal of the direction of motion of the hydraulic cylinder when the roof sections are in a certain position. In conventional hydraulic systems used in roof structures, a reversal of the direction of motion of the hydraulic cylinder would require reversing the direction of rotation of the motor of a hydraulic pump, which is difficult to implement. The prior-art roof may function more or less reasonably when the roof is being lowered into the folded-down stowage position as in this situation its operation is assisted by gravitation, whereas when the roof is being raised from the folded-down position into the closed position and a situation is reached where the direction of motion of the main actuating cylinder should be reversed with unfavorable leverages prevailing at the same time, the functionability of the prior-art roof is uncertain.
Yet another problem is that, as the entire roof structure is operated by means of a single main actuating cylinder, this cylinder has to be designed to relatively large dimensions and weight.
The object of the invention is to eliminate the above-mentioned drawbacks.
A specific object of the invention is to disclose a three-section hard roof having a structure as simple as possible, in which the turning motion of the forward roof section can be accomplished and timed independently of the operating mechanism of the rearward roof section and middle roof section so that the forward roof section can be turned in relation to the middle roof section when this is most advantageous.
As for the features characteristic of the convertible roof of the invention, reference is made to the claims.
According to the invention, the roof comprises a second actuator for turning the forward roof section in relation to the middle roof section separately and independently of positive mechanical control between the rearward roof section and the middle roof section.
The invention provides the advantage that the forward roof section can be turned by means of its own actuator, whose operation can be so adjusted that a roof completely reliable in operation is achieved. A further advantage of the invention is that the roof-actuating mechanism can be made simpler than before with fewer parts. A further advantage of the invention is that the main actuator can be designed to smaller dimensions and weight than before. Yet another advantage of the invention is that the leverages of the roof mechanism can be designed in a better way, allowing a light-construction roof to be achieved without the use of particularly strong materials. In addition, the forward roof section can be moved relative to the other roof sections during the opening and closing movements of the roof when this is most advantageous in respect of the stresses applied to the mechanism, the space utilization required by the opening and closing and in respect of the comfort of passengers present in the vehicle. A further advantage is that the main actuator needs to be operated in only one direction during the opening and closing movements of the roof.
In an embodiment of the roof, the second actuator is of a retractable/extendable type and comprises a first end, which is connected to the middle roof section, and a second end, which is connected to the forward roof section.
In an embodiment of the roof, the forward roof section and the middle roof section are pivotally connected to each other via a swivel joint. The roof comprises an actuating lever pivotally connected to the forward roof section at a distance from the swivel joint and pivotally connected to the middle roof section at a distance from the swivel joint. One end of the second actuator is pivotally connected to the actuating lever.
In an embodiment of the roof, the roof comprises a control lever, which is pivotally connected to the middle roof section at a distance from the swivel joint and pivotally connected to the actuating lever at a distance from the pivot between the actuating lever and the forward roof section, so that the pivots of the forward roof section, middle roof section, actuating lever and control lever together form a joint quadrangle mechanism.
In an embodiment of the roof, the second actuator is a hydraulic cylinder. The hydraulic cylinder comprises a piston rod pivotally connected to the actuating lever and a cylinder tube pivotally connected to the middle roof section. In another embodiment, the second actuator may be e.g. a torque motor. The second actuator may also consist of any other type of actuator known in itself, operated by a pressure medium or electricity and working in a linear or revolving manner.
In an embodiment of the roof, the second actuator has been arranged to turn the forward roof section into a position under and opposite to the middle roof section when the rearward roof section and middle roof section have been turned into a position where the rearward and middle roof sections are substantially above the boot so that the forward roof section can turn in the space behind and above the passenger compartment without interfering with the passengers.
In an embodiment of the roof, the forward roof section, the middle roof section and the rearward roof section are substantially of the same size so that, when folded one over the other, they take up a space substantially the size required by the length of one roof section.